Mark Strauss

Can a corporation claim to have religious beliefs? The Supreme Court will rule on that contentious question later this year. To answer, the justices may also have to address whether human life begins when an egg is fertilized, or when that egg is implanted in a womb.

The case, Sebelius vs. Hobby Lobby Stores Inc., is a challenge to the Obama administration's Affordable Care Act. Is a business required to provide its employees with health insurance that includes access to free birth control, even if doing so would violate the religious beliefs of the family that owns the business?

That's the legal issue. But, as Maggie Koerth-Baker points out in a recent essay, there's a second, separate question steeped in a conflict between science and religious belief. Hobby Lobby doesn't want to cover the cost of birth control that includes intrauterine devices (IUDs), because it claims that IUDs cause abortions.

Not so, say proponents of birth control. IUDs are used to prevent pregnancies, not terminate them. Yet, as Koerth-Baker explains, opponents of IUDs are mostly—though not entirely—incorrect.

The underlying issue is the definition of pregnancy. Biologists and doctors say it begins at implantation—when a fertilized egg attaches itself to the lining of the uterus. The owners of Hobby Lobby, however, believe that life begins when an egg is fertilized and argue that anything that interferes with implantation is abortion, since it prevents fertilized eggs from becoming viable pregnancies.

And that's why IUDs are controversial, says Koerth-Baker:

The bulk of evidence suggests that …. when you put an IUD in your uterus, your immune system registers it as an intruder and starts to attack. White blood cells can't kill a piece of plastic and copper, but they give it their best shot, and those efforts end up killing the majority of sperm that reach the uterus. The effect is even stronger in IUDs made with copper, like ParaGard, because copper ions are also toxic to sperm….

While we know IUDs do an impressive job of preventing fertilization, we also know that they're perfectly capable of preventing implantation, as well. ParaGard, the copper IUD, can be used as emergency contraception. Say you have sex, and the condom breaks. You can go in to the doctor the next day, or even as many as five days later, get a ParaGard, and almost eliminate your chances of getting pregnant. But sperm reach the fallopian tubes within minutes of ejaculation. So the IUD can't be working by killing off sperm….

If you go by the scientific definition, where pregnancy begins at implantation, then IUDs definitely don't work by causing abortions. If your religious beliefs lead you to think pregnancy begins at fertilization, well, the data suggests that, sometimes, rarely, IUDs used as birth control might abort a fertilized egg. In that way, everybody's right. But the science — what we know about IUDs from evidence — suggests that the primary mechanism is to prevent fertilization, not to prevent implantation. So, in that way, Planned Parenthood is more correct than Hobby Lobby, no matter what deeply held religious beliefs the company's owners may have.